ABSTRACT: The Air Force has identified a need for a high performance traveling wave tube amplifier (TWTA) that supports high data rate battlefield satellite communications (SATCOM) for the foreseeable future. We propose to develop a light-weight, power-efficient, compact TWTA capable of operating between 20.2 GHz and 21.2 GHz, with high linearity using our innovative solid state vacuum device (SSVD) approach that employs solid state integrated circuit design processes and techniques for fabricating the interaction circuit slow wave structure (SWS) to realize and achieve high performance including excellent efficiency, high linearity in a compact and lightweight TWTA. The SSVD TWTA to be designed, developed and implemented in this SBIR program shall be capable of delivering an output power>80 Watts with a gain of 55 dB (min) and gain flatness of 1.0 dB (max) at rated power, a voltage standing wave ratio (VSWR) of 2.5:1 (typ), Load VSWR 2.0:1 (max), harmonic content of 3 dBc or less, spur suppression of 50 dBc , saturated efficiency>60%, gain stability .25 dB/24 hrs, reliability consistent with 15-year satellite Mean Mission Duration (MMD), operating temperature range 40 deg C to +85 deg C, and radiation total dose tolerance>1Mrad(Si). BENEFIT: The high power high frequency regime has a number of potential applications. New technology in this part of the electromagnetic spectrum will directly benefit communications on the battlefield such as military"comms on the move,"personal and portable active denial systems, and other communications and data gathering and dispersal systems. Immediate application potential ranges broadly to include secure data links, video links, backhaul connections between cellular communications stations, space, radar, biological and chemical agent detection, atmospheric environment sensing, near object detection, and material imaging. The small size and weight, combined with high linearity and efficiency make this SHF TWTA a key building block for both military and commercial uses. The proposed design of the 20.2 to 21.3 GHz SHF TWTA can be relatively easily designed for other frequencies, power levels and applications. Areas of commercial market interest include the RF-based commercial satellite communications programs (e.g. Iridium, Globalstar and Spaceway), and commercial SATCOM broadcast programs including XM radio, Sirius Radio and DirectTV. Current and future commercial applications for these source products also include very high data rate transmissions including full duplex Ethernet connectivity, monitoring and detection systems for all-weather, day-and-night operations (i.e., mm-wave imaging, airport surveillance, intrusion detection, and harbor traffic monitoring), fusion plasma research and thermal interactions and processing of materials, and a host of other fundamental scientific, academic, and research applications.